The present invention relates to a texturized, combined polyester multifilament yarn and a process for producing the same. More particularly, the present invention relates to a texturized, combined polyester multifilament yarn comprising two or more types of texturized polyester multifilaments, different in polymer composition thereof from each other, combined with each other to form a combined yarn and having an enhanced bulkiness, and a process for producing the yarn.
Currently various types of texturized polyester multifilament yarns are produced from two or more types of polyester multifilaments different in elongation and/or thermal shrinkage from each other by draw-false twisting or drawing procedures in which the two or more different types of undrawn multifilaments are processed altogether. In this procedure, a difference in real filament length between the two or more different types of multifilaments is increased due to the differences in the elongation property and thermal shrinkage property between them, to thereby expand the gap spaces between the texturized individual filaments contained in the combined yarn and to enhance the bulkiness of the resultant texturized, combined multifilament yarn.
The term xe2x80x9creal filament lengthxe2x80x9d means a length of a filament in a straightened condition.
The two or more types of undrawn polyester multifilaments different in elongation and/or thermal shrinkage and usable for the production of the texturized multifilament yarn are briefly classified into the following two groups.
Group 1
Two or more different types of multifilaments are. melt-spun through melt-spinning orifices; and then the resultant undrawn multi-filaments are separately wound up around two or more different bobbins. These yarns are referred to as separately wound multifilament yarns.
Group 2
Two or more different types of multi-filaments are melt-spun through melt-spinning orifices; the resultant undrawn individual multifilaments are combined with each other; and the combined multifilaments are wound around a single bobbin. The yarn is referred to as a melt-spun, combined multifilament yarn.
The separately wound multifilament yarns (group 1) are advantageous in that since the melt-spun multifilament yarns are wound separately from each other, and thus the polymer composition of and yarn-production conditions for each yarn can be widely varied, variety in combinations of the different types of the multifilaments can be significantly enhanced. However, the separately wound multifilament yarns are disadvantageous in that, in the production of two or more different types of multifilament yarns, two or more separate apparatuses are necessary, and thus the productivity of the combined multifilament yarn is low. Also, the separately wound multifilament yarns are disadvantageous in that when the two or more different types of separately wound multifilaments are combined with each other to form a combined yarn, it is difficult to smoothly combine the individual multifilaments with each other during the texturized yarn-forming procedure, and the multifilaments which have a longer filament length and should be mainly located in an outer layer of the resultant texturized, combined multifilament yarn to serve as sheath filaments for the yarn, are not fixed around other multifilaments which have a shorter filament length and should be mainly located in an core portion of the resultant textured, combined multifilament yarn to serve as core filaments for the yarn, and thus the longer filament length sheath filaments do not contribute to sufficiently enhancing the bulkiness of the resultant texturized, combined multifilament yarn.
The melt-spun, combined multifilament yarn (group 2) is advantageous in that since a plurality of types of multifilaments are wound to form a single package, the combined multifilament yarn can be produced by a single melt-spinning apparatus; and since the plurality of types of the melt-spun multifilaments are combined before the winding procedure, the melt-spun individual multifilaments are easily combined with each other; and in the resultant texturized, combined multifilament yarn, the longer filament length multifilaments can be easily located in the outer layer of the resultant yarn to serve as sheath filaments and contribute to enhancing the bulkiness of the resultant yarn. However, since the melt-spun, combined multifilament yarn is produced by a single melt-spinning apparatus, the melt-spinning conditions, for a plurality of types of the multifilaments, are difficult to change widely and independently; large differences in the elongation property and shrinkage property are difficult to produce between the two or more types of the multifilaments; and thus production of a texturized, combined multifilament yarn in which the difference in real filament length between the two or more types of multifilaments is large enough to obtain a high bulkiness of the yarn, is difficult.
Japanese Unexamined Patent Publication No. 58-98418 discloses a process in which only the advantages of both the separately wound multifilaments and the melt-spun, combined multifilaments appear. In this process, a specific polymer, for example, a polymethyl methacrylate, is added to one type of multifilaments for a combined multifilament yarn, to thereby greatly increase the elongation of the polymethyl methacrylate-added multifilaments in comparison with that of the non-polymethyl methacrylate-added multifilaments, and thus a texturized combined multifilament yarn having a large difference in real filament length between two or more types of multifilaments, which large difference was believed to be unobtainable by the conventional melt-spun, combined multifilaments, can be obtained.
However, the inventors of the present invention studied the above-mentioned process and found that in a stage of the process in which a difference in the real filament length is created between the two or more types of melt-spun multifilaments, the combination of the individual melt-spun multifilaments with each other proceeds to an excessive extent, and thus the combined melt-spun individual multifilaments are restricted in the movement in relation to each other; thus, the longer filament length multifilaments are difficult to be located in the outer layer of the resultant combined yarn; and the resultant combined yarn exhibit an insufficient bulkiness, even when the filament length difference, per se, is large.
Japanese Unexamined Patent Publication No. 63-42,913 discloses a copolymerization of isophthalic acid into a polyester molecule chain, in place of an addition of polymethyl methacrylate. According to the publication, the copolymerization of isophthalic acid contributes to increasing the difference in shrinkage between two or more types of melt-spun multifilaments in the melt-spun, combined multifilament yarn and enables the resultant bulky texturized yarn to exhibit a large difference in the real filament length between the two or more types of multifilaments, similar to that in Japanese Unexamined Patent Publication No 58-98418. However, it has been found by the inventors of the present invention that in the production of the bulky texturized multifilament yarn of Japanese Unexamined Patent Publication No. 63-42913, in which isophthalic acid is employed, the melt-spun multifilaments are combined to an excessive extent in the stage of creating the difference in the real filament length between two or more types of multi-filaments, and thus the resultant texturized, combined multifilament yarn exhibits an unsatisfactory bulkiness even when a large filament length difference is created. Accordingly, the conventional art has not yet succeeded to provide a texturized, combined polyester multifilament yarn in which longer multifilaments are satisfactorily located in the outer layer of the yarn to form a bulky sheath layer, the difference in the filament length between two or more types of multifilaments is sufficiently large and the bulkiness of the resultant combined yarn is satisfactory.
An object of the present invention is to provide a texturized, combined polyester multifilament yarn in which a difference in filament length between two types of polyester multifilaments is large, and an outer layer thereof is mainly formed from polyester multifilaments having larger filament length to enable the resultant yarn to exhibit a high bulkiness, and a process for producing the bulky yarn.
The above-mentioned object can be attained by the textured, combined polyester multifilament yarn, and the process for producing the same, of the present invention.
The textured, combined polyester multifilament yarn of the present invention comprises two types of texturized polyester multifilaments FYA and FYB different in polymer chemical composition thereof from each other and combined and intermingled with each other to form a combined multifilament yarn FY, wherein average filament length under a straightened condition of the individual multifilaments FYB is 8 to 40% longer than that of the individual multifilaments FYA in the combined multifilament yarn FY, the shorter individual multifilaments FYA have a coefficient of variation (CVA) in filament length under straightened condition of 3% or less, and a coefficient of variation (CVBxe2x88x92A) in difference between the individual filament lengths of the longer individual multifilaments FYB and the average filament length of the shorter individual multifilaments FYA each under straightened condition is in the range of from 10 to 20%.
In the texturized, combined polyester multifilament yarn of the present invention, the longer multifilaments FYB preferably contain a filament elongation-enhancing agent in an amount of 0.5 to 5% by weight based on the weight of the polyester polymer contained in the longer multifilaments FYB.
In the texturized combined polyester multifilament yarn of the present invention, the filament elongation-enhancing agent preferably comprises an addition polymerization product of at least one unsaturated monomer, which product is substantially insoluble in the polyester in the longer individual filaments FYB and has a weight average molecular weight of at least 2000.
In the texturized, combined polyester multifilament yarn of the present invention, the polyester contained in the shorter individual multifilaments FYA preferably contains, as a portion of a residue of a dicarboxylic acid component for forming the polyester, isophthalic acid residue in an amount of 3 to 15 molar % of the total content of dicarboxylic acid residues.
In the texturized combined polyester multifilament yarn of the present invention, the longer polyester multifilaments FYB preferable have an average individual filament thickness corresponding to 80% or less of that of the shorter polyester multifilaments FYA, and the number of the longer polyester multifilaments FYB is preferably at least 1.5 times that of the shorter polyester multifilaments FYA, per one combined ultifilament yarn FY.
The process of the present invention for producing a texturized, combined polyester multifilament yarn, comprises the steps of:
separately melt-spinning two types of polyesters, different in chemical composition from each other, respectively through melt-spinning holes for the two types of polyesters to separately provide two types of undrawn polyester multifilaments;
combining the two different types of multifilaments with each other, while subjecting the two different types of multifilaments to a filament-intermingling treatment in which an air blast is applied to the combined multifilaments under an air pressure of 50 to 600 kPa, to intermingle the individual multifilaments with each other;
taking up the resultant combined, intermingled multifilament bundle;
drawing the multifilament bundle at a draw ratio of 1.2 to 2.5, to provide a combined, intermingled and drawn multifilament yarn comprising two types of drawn multifilament different in thermal shrinkage from each other; and
applying a heat texturizing treatment to the drawn multifilament yarn to such an extent that a type of resultant texturized multifilaments FYB have an average filament length under straightened condition of 8 to 40% longer than that of the other type of the resultant texturized multifilaments FYA, in the resultant multifilament yarn FY, the shorter individual multifilaments FYA exhibits a coefficient of variation (CVA) in filament length under straightened condition of 3% or less, and a coefficient of variation (CVBxe2x88x92A) in difference between the filament lengths of the longer individual multifilaments FYB and the average filament length of the shorter individual multifilaments FYA each under straightened condition is in the range of from 10 to 20%.
In the process of the present invention, the air filament-intermingling treatment is preferably effected by an interlace method.
In the process of the present invention, the spinning holes for the two types of polyesters are preferably formed in one single spinneret plate. Best Mode of Carrying out the Invention
The inventors of the present invention have made an extensive study for attaining an appropriate combination of the two different types of melt-spun polyester multifilaments contained in the melt spun, combined multifilament yarn before taking up and winding the combined yarn. As a result, it was found that during the melt-spinning, combining procedures (before the taking up and winding procedures), an application of an air blast to the combined multifilaments under an air pressure of 50 to 600 kPa contributes to intermingling the combined multifilaments with each other and to controlling the degree of combination to an appropriate level, and the resultant texturized, combined polyester multifilament yarn exhibits a high bulkiness. The special filament-intermingling treatment under a specific air blast pressure of the present invention is new and the advantages derived from the special filament-intermingling treatment were not known in the prior art.
The texturized, combined polyester multifilament yarn of the present invention comprises two types of texturized polyester multifilaments FYA and FYB different in polymer chemical composition thereof from each other and combined and intermingled with each other to form a combined multifilament yarn FY. The difference in polymer chemical composition includes differences in the type and content of the recurring units of the polyester molecules, the type of additives contained in the polyester resin and the type and content of comonomers.
In the texturized, combined polyester multifilament yarn FY, the average length of the individual multifilaments FYB in a straightened form is 8 to 40% longer than that of the individual multifilaments FYA in a straightened form. The difference in the average filament length between the texturized multifilaments FYA and FYB in the texturized, combined multifilament yarn FY is defined by the following equation.       Δ    ⁢          xe2x80x83        ⁢    L    ⁢          xe2x80x83        ⁢          (      %      )        =                              (                      L            B                    )                -                  (                      L            A                    )                            (                  L          A                )              xc3x97    100  
wherein xcex94L represents a difference in average filament length between the texturized multifilaments FYB and FYA each in straightened form and contained in the texturized, combined multifilament yarn FY having a certained length, LB represents an average filament length of the longer texturized multifilaments FYB in straightened form, and LA represents an average filament length of the shorter texturized multifilament FYA in straightened form.
The xcex94L may be referred to as an average filament length difference.
The texturized, combined multifilament yarn FY of the present invention has a core portion formed mainly from the texturized shorter multifilaments FYA and an outer (sheath) layer surrounding the core portion and mainly formed from the texturized longer multifilaments FYA, the shorter and longer multifilaments FYA and FYB are partially intermingled with each other to form a combined multifilament yarn.
When the average filament length difference is less than 8%, the texturized longer multifilaments FYB mainly located in the sheath layer cannot form large spaces between the individual multifilaments FYB and FYA sufficient to impart a high bulkiness to the combined multifilament yarn. Also, when the average filament length difference is more than 40%, connecting points between the texturized shorter multifilaments FYA mainly located in the core portion and the texturized longer multifilaments FYB mainly located in the sheath layer are decreased and as a result, the sheath layer cannot be fixed around the core portion of the combined multifilament yarn, and the individual multifilaments in a plurality of combined yarns brought into contact with each other are easily intertwined with each other. This intertwining phenomenon is referred to as xe2x80x9ca fastener phenomenonxe2x80x9d. The average filament length difference is preferably 10 to 30%.
In the texturized, combined polyester multifilament yarn of the present invention, the problems, namely an unsatisfactory bulkiness, of the prior art combined multifilament yarns produced from the melt-spun, combined multifilament yarn are completely solved.
In the texturized, combined polyester multifilament yarn FY of the present invention, the shorter individual multifilaments FYA have a coefficient of variation (CVA) in filament length under straightened condition of 3% or less, and a coefficient of variation (CVBxe2x88x92A) in difference between the average filament length of the longer individual multifilaments FYB and the shorter individual multifilaments FYA each under straightened condition is in the range of from 10 to 20%.
The coefficient of variation CVBxe2x88x92A in % is determined by the following measurement.
A sample of the texturized, combined multifilament yarn FY is cut to 5 cm length, the texturized shorter and longer multifilaments FYA and FYB in the yarn FY are separated from each other. Differences in filament length between 50 longer multifilaments FYB and 50 shorter multifilaments FYA are measured, and an average filament length difference is calculated from the measurement data. Also, a standard deviation of the measured differences between the individual filament lengths of the longer individual multifilaments FYB and the average filament length of the shorter individual multifilaments FYA is calculated. The coefficient of variation CVBxe2x88x92A is a quotient in % of the standard deviation of the filament length differences between the longer and shorter multifilaments FYB and FYA divided by the average filament length difference. In the present invention, the CVBxe2x88x92A must be 10 to 20%. For reference, the CVBxe2x88x92A of the texturized combined polyester multifilament yarn disclosed in Example 1 of Japanese Unexamined Patent Publication No. 58-98418 using melt-spun, combined multifilament yarns is 28%, and the CVBxe2x88x92A of the texturized, combined polyester multifilament yarn formed from separately wound multifilaments is 8%.
When the CVBxe2x88x92A is more than 20%, the shorter and longer multifilaments FYA and FYB are combined to an excessive extent, and thus are excessively restricted in movement thereof with each other. Thus even when the filament length difference between the multifilaments FYA and FYB is large, the spaces formed between the multifilaments FYA and FYB are not large enough to enable the resultant combined multifilament yarn to exhibit a high bulkiness. Also, when the CVBxe2x88x92A is less than 10%, the shorter and longer multifilaments FYA and FYB are insufficiently combined with each other and thus the sheath layer mainly formed from the longer multifilaments FYB are not firmly fixed to the core portion formed mainly from the shorter multifilaments FYA. Namely, the sheath layer easily slips out from the core portion of the combined multifilament yarn.
In the present invention, an unexpected advantage such that the resultant texturized, combined multifilament yarn of the present invention produced from the melt-spun, combined multifilament yarn containing two types of multifilaments exhibits a higher bulkiness than that of the conventional texturized, combined multifilament yarn produced from two types of separately wound multifilaments having the same average filament length difference as that of the present invention. Namely, in the present invention, the control of the combination degree of the two different types of multifilaments by applying the air blast treatment enables not only the two different types of multifilaments in the melt-spun, combined multifilament yarn to be combined with each other in an appropriate condition close to that of the separately wound multifilament yarn, but also enables the resultant texturized, combined multifilament yarn to exhibit a higher bulkiness than that produced from the separately wound multifilament yarns.
The mechanism of creating the high bulkiness of the texturized, combined multifilament yarn is not fully clear. The mechanism is, however, assumed to be as follows.
Namely, in the case where the separately wound multifilament yarns are employed, the resultant texturized combined multifilament yarn has large spaces formed between the multifilaments FYA and FYB, but since the filament length of the multifilaments FYB mainly located in the sheath layer is uniform, the above-mentioned spaces are concentrated between the core portion and the sheath layer of the combined multifilament yarn, the sheath layer mainly formed from the longer multifilaments FYB around the core portion cannot maintain the surrounding layer around the core portion and approaches the core portion so that the spaces between the sheath layer and the core portion are lost. In the texturized, combined multifilament yarn of the present invention, since the filament length of the longer multifilaments FYB is distributed in an appropriate range, the spaces formed between the multifilaments FYA and FYB are not concentrated between the sheath layer and the core portion of the combined multifilament yarn, and thus the spaces formed between the multifilaments FYA and FYB due to the filament length difference can be utilized to the maximum. The larger the filament length difference between the shorter and longer multifilaments FYA and FYB, the higher the restriction effect for concentration of the spaces between the sheath layer and the core portion. Thus, in view of the above-mentioned fact, the average filament length difference between the shorter and longer multifilaments FYA and FYB is preferably 10 to 30%.
The shorter multifilaments FYA are mainly located in the core portion of the combined multifilament yarn. Thus, when a stretching load is applied to the texturized, combined multifilament yarn, the shorter multifilaments FYA serve as a stress-carrier. Therefore, the scattering in the filament length of the shorter multifilaments FYA is preferably as small as possible. When a sample of the texturized, combined polyester multifilament yarn is cut into a length of 5 cm, and the filament length of the shorter multifilaments in straightened form is measured, the coefficient of variation (CVA) in the filament length under straightened condition of the shorter individual multifilaments FYA is controlled to 3% or less.
The polyester resin usable for the present invention is preferably selected from polyethylene terephthalate, polytrimethylene terephthalate, polytetramethylene terephthalate, polyethylene-2,6-naphthalate and copolymers of two or more of the component monomers of the above-mentioned polyesters and mixtures of two or more of the above-mentioned polyesters and copolymers. More preferably, the polyester usable for the present invention is selected from polyesters containing recurring ethylene terephthalate units in an content of 80 molar % based on the total molar recurring unit amount, which polyester is easily formed into filaments. Also, the polyester resin may contain at least one additive selected from delustering agents, pigments, flame retardants, deodorizers, antistatic agents, antioxidants and ultraviolet ray-absorbing agents, unless the additive hinders the attainment of the object of the present invention.
To obtain a satisfactory filament length difference between the longer and shorter multifilaments YFB and YFA, preferably, the longer multifilaments FYB contains a filament elongation-enhancing agent for enhancing the elongating property of the multifilaments FYB, and the shorter multifilaments FYA contains a filament shrinkage-enhancing agent for increasing the thermal shrinking property of the multifilament FYA.
The multifilaments FYB containing the filament elongation-enhancing agent are preferably employed in combination with the multifilaments FYA containing the filament shrinkage-enhancing agent.
The filament elongation-enhancing agent is contained in an amount of 0.5 to 5% by weight based on the polyester resin weight of the longer multifilaments FYB. If the content of the filament elongation-enhancing agent is less than 0.5% by weight, the filament elongation enhancing effect on the longer multifilaments FYB may be insufficient and thus a satisfactory filament length difference between the shorter and longer multifilaments FYA and FYB may not be obtained. Also, if the content of the filament elongation-enhancing agent is more than 5% by weight, the filament elongation effect on the longer multifilaments FYB may be saturated, breakages of the multifilaments during the melt spinning procedure may increase so that the production procedure of the combined yarn may be unstable. The filament elongation-enhancing agent may be contained in a small amount in the shorter multifilaments FYA. The content of the filament elongation-enhancing agent in the shorter multifilaments FYA is preferably limited to a level of 1.5% by weight or less and of 0.5% by weight below the content of the filament elongation-enhancing agent in the longer multifilaments FYB.
The filament elongation-enhancing agent preferably comprises an addition polymerization product of at least one unsaturated monomer, which product is substantially insoluble in the polyester in the longer individual filaments FYB and has a weight average molecular weiaht of at least 2000. If the filament elongation-enhancing agent is soluble in the polyester and/or the molecular weight of the agent is less than 2000, a satisfactory filament elongation-enhancing effect on the longer multifilaments FYB may not be obtained.
The addition polymerization products of the unsaturated monomer usable for the filament elongation-enhancing agent are preferably selected from polymethacrylate polymers, polyacrylate polymers, poly(4-methyl-1-pentene)polymers, polyoctadecene-1 polymers and polyvinyl benzyl polymers styrene polymers and styrene derivative polymers. Preferably, the filament elongation-enhancing agent has a thermal deformation temperature of 110 to 130xc2x0 C., which is higher than the glass transition temperature of the polyester, and which causes that when the polyester melt containing the filament elongation-enhancing agent is extruded through a melt-spinning orifice, the filament elongation-enhancing agent contained in the extruded filamentary polyester melt stream can be solidified in an upstream portion of the melt-spinning path. If the thermal deformation temperature is less than 110xc2x0 C., the difference between the thermal deformation temperature and the glass transition temperature of the polyester is small, and thus the filament elongation-enhancing effect on the multifilaments FYB is low. Also if the thermal deformation temperature is higher than 130xc2x0 C., the filament elongation-enhancing agent contained in the filamentary polyester melt stream extruded through the melt-spinning orifice is rapidly solidified immediately after passing through the melt-spinning orifice, thus the solidification of the polyester melt does not occur at the same time as the solidification of the filament elongation-enhancing agent, and this phenomenon causes the breakages of the extruded filamentary polyester melt streams to increase. The filament elongation-enhancing agent usable for the present invention is disclosed in WO 99/47735.
To enhance the thermal shrinkage of the shorter multifilaments FYA, preferably the dicarboxylic acid residue contained in the shorter multifilaments FYA is substituted in an amount of 3 to 15 molar %, based on the total content of the dicarboxylic acid residue by a bisphenol A residue, a isophthalic acid residue or a residue of a derivative of bisphenol A or isophthalic acid, having at least one metal sulfonate salt group attached, as a side chain, to the aromatic group of the bisphenol A or isophthalic acid.
If the content of the substituent is less than 3 molar %, the filament shrinkage-enhancing effect on the shorter multifilaments FYA may be unsatisfactory. Also, if the substitution is more than 15 molar %, the filament shrinkage-enhancing effect may be saturated and the breakages of the filaments during the melt-spinning procedure may increase.
The above-mentioned filament elongation-enhancing agent may be contained in the shorter multifilaments FYA and the above-mentioned filament shrinkage-enhancing means may be applied to the longer multifilaments FYB, as long as the satisfactory filament length difference between the shorter and longer multifilaments FYA and FYB is obtained. Also, as long as the requirements on the CVA of the shorter multifilaments FYA and the CVBxe2x88x92A between the longer and shorter multifilaments FYB and FYA are satisfied, the multifilaments FYA or FYB may contain those having an irregular cross-sectional profile or may contain two or more types multifilaments different in thickness from each other.
When the texturized, combined polyester multifilament yarns of the present invention are employed to produce a fabric, the sheath layers of the yarn mainly formed from the longer multifilaments FYB impart a soft hand to the resultant fabric, and the core portions of the yarns mainly formed from the shorter multifilaments FYA imparts a hard hand (or rigid hand or elastic hand) to the fabric. Thus, preferably, the thickness of the individual longer multifilaments FYB is 80% or less of the thickness of the individual shorter multifilaments FYA, and the number of the individual filaments of the longer multifilaments contained in a yarn is at least 1.5 times that of the shorter multifilaments FYA. More preferably, the longer multifilaments FYB have an individual filament thickness of 0.5 to 1.5 dtex and have a number of filaments per yarn of 24 to 96. Also, preferably, the shorter multifilaments FYA have an individual filament thickness of 1 to 6 dtex and the number of filaments per yarn of 12 to 36.
In the texturized, combined polyester multifilament yarn of the present invention, in the case where the yarn is a non-crimped yarn or a crimped yarn having a low percentage of crimp of less than 2%, the number of intermingling points, of the multifilaments FYA and FYB, is preferably 30 to 60 per meter of the yarn. In the case where the percentage of crimp of the yarn is 2 to 12%, the intermingling point number is preferably 15 to 40 per m of the yarn. When the percentage of crimp of the yarn is less than 2%, the resultant yarn is free from a rough hand and has a very soft hand, but slippage between the sheath layer-forming filaments and the core portion-forming filaments occurs easily. Therefore, in this case, the intermingling point number is preferably 30 or more per m of the yarn. However, if the intermingling point number is more than 60 per m of the yarn, the resultant yarn may exhibit stiff hand. Where the percentage of crimp of the yarn is 2 to 12%, the crimp of the yarn causes the bulkiness of the yarn to increase and thus the resultant yarn exhibits a significantly enhanced bulkiness. Also, the crimps cause slippage between the sheath layer-forming filaments and the core portion-forming filaments to be restricted in comparison with the non-crimped yarn. Thus, in this case, the intermingling point number is preferably in the wide range of from 15 to 40 per m of the yarn.
The process of the present invention for producing the texturized, combined polyester multifilament yarn will be explained below.
The process of the present invention comprises the steps of:
separately melt-spinning two types of polyesters different, in chemical composition, from each other respectively through melt-spinning holes for the two types of polyesters to separately provide two types of undrawn polyester multifilaments;
combining the two different types of multifilaments with each other, while subjecting the two different types of multifilaments to a filament-intermingling treatment in which an air blast is applied to the combined multifilaments under an air pressure of 50 to 600 kPa, to intermingle the individual multifilaments with each other;
taking up the resultant combined, intermingled multifilament bundle;
drawing the multifilament bundle at a draw ratio of 1.2 to 2.5, to provide a combined, intermingled and drawn multifilament yarn comprising two types of drawn multifilament different in thermal shrinkage from each other; and
applying a heat texturizing treatment to the drawn multifilament yarn to such an extent that a type of resultant texturized multifilaments FYB have an average filament length under straightened condition of 8 to 40% longer than that of the other type of the resultant texturized multifilaments FYA, in the resultant multifilament yarn FY, the shorter individual multifilaments FYA exhibit a coefficient of variation (CVA) in filament length under straightened condition of 3% or less, and a coefficient of variation (CVBxe2x88x92A) in difference between the filament lengths of the longer individual multifilaments FYB and the average filament length of the shorter individual multifilaments FYA, each under a straightened condition, is in the range of from 10 to 20%.
In the process of the present invention, it is important that a filament-intermingling treatment using an air blast under an air pressure of 50 to 600 kPa is applied to the combined multifilaments, to intermingle the individual multifilaments with each other and to control the combination of the two different types of multifilaments to an appropriate degree.
In the process of the present invention, two types of polyester resins different in chemical composition from each other are separately melt-spun through melt-spinning holes for the two different types of polyester resins to provide two types of undrawn, non-bundled polyester multifilaments different in chemical composition and thus elongation and thermal shrinkage from each other. Then, the two types of melt-spun, undrawn, multifilaments are unbundled and are combined with each other to provide a combined multifilament bundle. In this process, before the combining procedures, the two types of separately melt-spun multifilaments are unbundled and thus, in the combining procedure, the two types of multifilaments can be evenly mixed with each other. If each type of melt-spun multifilaments are bundled before the combining procedure, the two types of the multifilaments cannot be evenly mixed with each other in the combining procedure. This phenomenon is similar to that occurring in the conventional process using the separately wound multifilament yarns which are independent from each other.
Then, in the process of the present invention, during the combining procedure, an air blast is applied to the two different types of multifilaments under an air pressure of 50 to 600 kPa, to intermingle the combined individual multifilaments with each other, to disturb the even combination of the two types of multi-filaments and to intermingle the individual multifilaments with each other. If the two different types of melt-spun multifilaments are combined, the combined multifilaments are taken up, and then the combined multifilaments are subjected to the filament-intermingling treatment with the air blast, the resultant combined, intermingled multifilament yarn exhibits the a CVBxe2x88x92A similar to that in a texturized, combined multifilament yarn produced from the conventional melt-spun, combined multi-filament yarns without applying the filament-intermingling treatment with the air blast. The change in the combining condition of the combined two different types of multifilaments due to the position at which the filament-intermingling treatment with the air blast is not fully clarified. However, in the case where the two different types of polyester resins are separately melt-spun, and the resultant two different types of multifilaments are taken up through a first godet roll and then wound through a second godet roll by a winder, the following is assumed.
When the filament-intermingling treatment with the air blast is applied upstream to the first godet roll, the melt-spun multifilaments are incompletely bundled by a filament guide, because if they are completely bundled, too high a friction between the filament guide and the filament bundle is generated, and thus the individual multifilaments are spaced from each other to a certain extent, and then the filament-intermingling treatment with the air blast is applied to the multifilaments. Thus the evenly combined condition of the two different types of melt-spun multifilaments is disturbed. In other words, the filament-intermingling treatment with the air blast serves to regularly arrange the multifilaments FYA in the core portion and the multifilaments FYB in the sheath layer of the combined multifilament bundle.
If the filament-intermingling treatment with the air blast is applied downstream of the first godet roll, the multifilaments are pressed to the first and second godet rolls, and thus the movements of the individual multifilaments relative to each other are restricted and the spaces between the individual multifilament are decreased. In other words, the density of the multifilament bundle is increased. When the filament-intermingling treatment by the air blast is applied to the dense multifilament bundle, due to an interference of the multifilaments to each other, the rearrangement of the multifilaments is hindered and thus the multifilament bundle is maintained in a uniformly combined condition.
Also, in the process of the present invention the pressure of the air blast applied to the two different types of multifilament in the combining procedure is important. If the air blast pressure is less than 50 kPa, even when the two different types of multifilaments are loosely bundled, the rearrangement of the multifilaments in the loose bundle cannot be sufficiently effected, and the combining condition of the two different types of multifilaments is made more uniform.
When the air blast pressure is more than 600 kPa, the rearrangement effect on the multifilaments is saturated, and the multifilament bundles are significantly vibrated to cause fluffs to be formed and filament breakage to occur. In the process of the present invention, the filament-intermingling treatment using the air blast is preferably carried out by a interlacing method.
The process of the present invention will be further explained below. The melt-spun multifilaments are produced by the following procedures.
The melt-spinning holes for the two different types of the multifilaments may be formed in two separate melt-spinnerets as long as the two different types multifilaments melt-spun through the separate spinnerets can be combined to form a multifilament bundle without separately bundling two different types of multifilaments and combining the bundled two different types of multifilaments into a yarn. However, preferably, the melt-spinning holes for two different types of multifilaments are formed in one single melt-spinneret. In this case, the two different types of melt-spun multifilaments are easily combined with each other before bundling, and the number of the mult-spinnerets can be reduced by half.
The polyesters usable for producing the two different types of multifilaments are as mentioned above. When a filament elongation-enhancing agent is mixed into a polyester resin for the longer multifilaments FYB to increase the elongation property of the longer multifilament FYB, preferably, the ultimate elongation of one type of undrawn multifilaments is controlled to 1.5 times, or more, more preferably 2 to 3.5 times, that of the other one undrawn multifilaments. If the ultimate elongation ratio is less than 1.5, it may be difficult to control the filament length difference between the shorter multifilaments FYA and the longer multifilaments FYB to a level sufficient to attain the object of the present invention, during the drawing and heat treatment procedures.
The procedure for producing a drawn, combined multifilament yarn will be explained below. The drawing procedure can be carried out by a draw-false twisting method in which a drawing procedure and a false twisting procedure are simultaneously applied to a undrawn, combined multifilament yarn or by a drawing method in which a false twisting procedure is not applied to the yarn. The draw-false twisting method is preferably applied to the undrawn, combined multifilament yarn in which two types of undrawn multifilaments are different in elongation property, and the drawing method is preferably applied to the undrawn, combined multifilament yarn in which two types of undrawn multifilaments are different in both elongation property and thermal shrinkage property. In the drawing procedure, in either method, the draw ratio is controlled to 1.2 to 2.5, preferably 1.5 to 2.3, to cause the resultant texturized, combined polyester multifilament yarn to have a satisfactory average filament length difference between the shorter and longer multifilaments. The draw-false twisting method for the undrawn, combined multifilament yarn of the present invention can be carried out under conventional conditions by using conventional apparatus. For example, a heating means may be arranged only upstream of the false twisting device, or another heating means may be further arranged downstream from the false twisting device, to relax the crimps of the yarn formed by the false twisting procedure.
In both the draw-false twisting procedure and the drawing procedure including no false twisting treatment, before or after the procedure, an additional filament-intermingling treatment using air blast may be applied to the yarn, unless this treatment causes the resultant textured, combined multifilament yarn to exhibit a degraded hand. After the combining procedure and the filament-intermingling treatment are simultaneously applied to the melt-spun multifilaments, the individual multifilaments are difficult to be rearranged. Thus, the additional filament-intermingling treatment contributes to enhancing the intermingle of the multifilaments with each other without causing the sheath layer to slip from the core portion of the combined yarn, before or after the drawing procedure.
In the drawn, combined multifilament yarn, the two types of multifilaments are different in thermal shrinkage from each other.
In the process of the present invention, the drawn, combined multifilament yarn is subjected to a heat texturizing treatment which is carried out to such an extent that the resultant texturized multifilaments FYB have an average filament length under straightened condition of 10 to 40% longer than that of the other resultant texturized multifilaments FYA, in the resultant multifilament yarn FY, the shorter individual multifilaments FYA exhibit a coefficient of variation (CVA) in filament length under straightened condition of 3% or less, and a coefficient of variation (CVBxe2x88x92A) in difference between average filament length of the longer individual multifilaments FYB and the shorter individual multifilaments FYA, each under straightened condition, is in the range of from 10 to 20%.
The heat texturizing treatment contributes to improving the weaving and knitting property of the texturized, combined multifilament yarn of the present invention.
After the texturized, combined multifilament yarn of the present invention is subjected to a weaving or knitting procedure, the resultant woven or knitted fabric is preferably subjected to a heat treatment in a hot water at a temperature of 60xc2x0 C. or more, preferably 70 to 130xc2x0 C., or in a wetted air atmosphere at a temperature of 80 to 120xc2x0 C. or in a dry air atmosphere at a temperature of 80 to 150xc2x0 C., preferably in a relaxed condition.
In the case where a filament elongation-enhancing agent is contained in the longer multifilaments FYB, and a drawing procedure free from a false twisting treatment is applied, preferably, before the above-mentioned heat treatment, an additional heat treatment is applied to the woven or knitted fabric on a plate heater at a temperature of about 190xc2x0 C. under a relaxed condition under which the fabric is allowed to shrink at a shrinkage of 2 to 5%, to allow the longer multifilaments to spontaneously elongate during the additional heat treatment. This additional heat treatment contributes to further enhancing the bulkiness of the resultant woven or knitted fabric.